A clutch release bearing is incorporated in a clutch device mounted between an engine and a transmission of an automobile. With respect to this clutch release bearing, there are the outer ring-rotating/inner ring-fixed type in which an outer ring rotates in contact with a rotating member of a clutch mechanism such as a diaphragm spring and the outer ring-fixed/inner ring-rotating type in which an inner ring rotates in contact with a rotating member of a clutch mechanism.
When water intrudes into the interior of this clutch release bearing, lubricating oil such as grease sealed in the interior of the bearing is deteriorated, and rust develops within the bearing, thus inviting a shortened life of the bearing.
Therefore, among clutch release bearings, there is the type employing a sealing structure constructed such that in order to prevent foreign matters such as water from intruding from the exterior of the bearing into the interior of the bearing and also to prevent lubricating oil such as grease sealed in the interior of the bearing from flowing to the exterior of the bearing, a seal fixed to one of an inner ring and an outer ring and held in contact or out of contact with the other is disposed between the inner ring and the outer ring at both ends in an axial direction.
Sealing structures of an outer ring-rotating/inner ring-fixed clutch release bearing are described in JP-A-2006-189086 Publication (Patent Literature 1) and JP-A-2001-311437 Publication (Patent Literature 2) serving as prior art literature. In the clutch release bearing described in Patent Literature 1, a seal member fixed to an inner ring and disposed in sliding contact with an outer ring is provided at the front side where a rotating member of a clutch mechanism is provided. And, a seal member fixed to the outer ring and disposed in sliding contact with the inner ring is provided at the opposite side, that is, the rear side in the axial direction. Also, with respect to an outer ring-rotating/inner ring-fixed clutch release bearing, a sealing structure constructed such that a seal member fixed to an outer ring is disposed in sliding contact with an inner ring is described in JP-A-2006-9826 Publication (Patent Literature 3).
A fragmentary cross-sectional view of a clutch release bearing 210 generally identical in construction to the clutch release bearing described in Patent Literature 1 is shown in FIG. 9.
The clutch release bearing 210 is the type of clutch release bearing comprising an outer ring 220 at which a radially inwardly-extending rib 222 having a convexly arc-shaped surface is formed, an inner ring 230 at which a radially inwardly-extending flat rib 232 is formed, and a plurality of rolling elements 214 rollably received between the inner ring 230 and the outer ring 220, and the outer ring 220 rotates by contact of a rotating member 212 of a clutch mechanism and the rib 222 of the outer ring 220 with each other.
And, the construction is such that at the front side where the rib 222 of the outer ring 220 is formed, a seal 250 is provided in abutting relation to a side face of the rib 232 of the inner ring 230, and a side lip 252 integrally joined to the seal 250 is disposed in sliding contact with the rib 222 of the outer ring 220. And, the construction is such that at the rear side opposite in an axial direction from that side where the rib 222 of the outer ring 220 is formed, a seal 240 is provided in internally-fitted relation to an inner peripheral surface of the outer ring 220, and a seal lip 242 formed at a distal end of the seal 240 is disposed in sliding contact with an outside-diameter surface of the inner ring 230. Therefore, the clutch release bearing 210 has such a structure that lubricating oil is less liable to leak and that muddy water is less liable to intrude, and therefore it is thought that the good lubricating ability and water resistance can be maintained.